https://www.ifixit.com/Teardown/iPhone+7+Plus+Teardown/67384
Step 13 confirms Qualcomm MDM9645M radio, thus 4x4 MIMO and 256QAM support in at least one of the models. Hopefully both models are actually Qualcomm radios this year, with the VZW/Sprint model enabling CDMA. Otherwise, the TMo version won't support their latest updates if it has an Intel radio, but the VZW/Sprint model will.
Step 13 confirms Qualcomm MDM9645M radio, thus 4x4 MIMO and 256QAM support in at least one of the models. Hopefully both models are actually Qualcomm radios this year, with the VZW/Sprint model enabling CDMA. Otherwise, the TMo version won't support their latest updates if it has an Intel radio, but the VZW/Sprint model will.